What improvement does tempering provide to hardened metal?

Tempering is a heat treatment process applied to hardened metals, particularly steel, to enhance their properties. When metal is hardened, it generally becomes very strong but may also become brittle. During tempering, the metal is reheated to a temperature below its critical point, followed by cooling. This process allows for the reduction of internal stresses that were introduced during the hardening process and promotes the movement of dislocations within the metal's crystal lattice.

The main improvement that tempering provides is increased toughness. Toughness refers to a material's ability to absorb energy and deform plastically without fracturing. By undergoing tempering, the metal retains much of its hardness while gaining better resilience against impact and stress. This results in a material that is less likely to fail under unpredictable loading conditions, making it suitable for applications where both strength and toughness are essential.

Thus, tempering strikes a balance between strength and ductility, allowing hardened steel to perform better in various structural applications.